Geographic Range

Periodical cicadas (members of the genus Magicicada) are only found in the United States, east of the Great Plains. Magicicada septendecim is found in the eastern, western, and especially northern parts of this area, thus being primarily located in the northern midwestern and eastern United States (Simon 1996).

Habitat

The majority of the life of Magicicada septendecim is spent in an underground or subterranean habitat. The area in which a periodical cicada brood is located must contain a large population of deciduous trees, on whose roots the cicadas feed during the underground nymph stages. The trees are also necesary for the molt into adulthood, choruses, and egg-laying (Boyer 1996).

Physical Description

Like all adult members of the Magicicada genus, Magicicada septendecim is black in color and about 1.5 inches in length. Its eyes and legs are generally reddish-orange, and the wings are clear with orange veins. Magicicada septendecim is the largest Magicicada species. Characteristics that distinguish the species from other Magicicada species include broad orange stripes on the abdominal underside and an orange spot on the side of the thorax (Road 1991, Cooley and Marshall 1997).

Reproduction

The17-year life cycle of Magicicada septendecim is of critical importance to its reproductive behavior. All members of the genus Magicicada remain in groups known as broods. In the case of M. septendecim, single brood emerges from underground together once every 17 years . In a year when a given brood has emerged to reproduce, female Magicicada septendecim mature and lay eggs in the twigs of trees. Hatching occurs during the middle of the summer, and the nymphs burrow one to three meters underground. Magicicada septendecim nymphs remain underground for 17 years, feeding and going through several juvenile stages. In the spring of the 17th year, the nymphs build exit tunnels, and generally emerge during the month of May. An entire brood sometimes emerges during one night. The nymphs then attach themselves to the bark of a nearby tree and undergo one final molt, becoming adults. Within four or five days of emergence, the males form singing choruses, as the females wait nearby. The males alternate between singing and flying until they find a female of their species willing to mate. Mating is achieved through copulation, and both males and females generally mate with several partners during the period. After a female has mated, she uses her needle-like egg-laying mechanism, called an ovipositor, to make small slits in twigs, where the eggs are to be layed. A single female can lay up to 500 eggs, and after this process, the female drops to the ground and dies. Neither the male nor the female lives past early July. The new nymphs, about 2.5 mm in length, hatch and journey to the ground, and the 17-year cycle begins anew (Cooley and Marshall 1997, Boyer 1996, Alexander 1990).

Behavior

All Magicicada species remain within large broods. It is generally accepted that brooding behavior exists mainly to "overwhelm" predators. The logic is that with such a large population in a relatively small area, even if many individuals are preyed upon, the mating population will still be sufficiently large so that many individuals will survive to reproduce. Brooding behavior, however, is rarely perfect. In a phenomenon known as straggling, a group of cicadas will emerge in a year not corresponding with the cycle of its brood. Straggling is most common during the years immediately before and after a broods emergence year, but can occur during other years. It is most common for a straggling emergence to involve only a few cicadas, but incidents of up to several thousand straggling individuals have occured.
Singing behavior is also of central importance. Only males can produce songs, and they do so with a pair of rigid membranes (called tymbals) near the abdomen. Singing behavior relates to mating, and is typically carried out in large choruses of males (see above). Each Magicicada species has an alarm call (commonly given when handled by a human), a calling song which attracts other individuals to a chorus, and three courtship calls. The songs and calls of each species are different, probably to allow differentiation during mating, since every brood contains members of several species. The calling song of Magicicada septendecim is said to sound like the word "Pharaoh"(Cooley and Marshall 1997).

Food Habits

Magicicada septendecim spends the vast majority of its 17-year life underground, in several juvenile stages, where it feeds by sucking juices from the roots of plants, especially deciduous trees (Boyer 1996). Although the majority of time during the adult portion of the cicada's life is spent engaging in reproductive behavior, the adults do feed by sucking fluids out of trees (Cooley and Marshall 1997).

Economic Importance for Humans: Positive

The very long life cycle and emergence in broods of Magicicada septendecim and related species is a relatively unique and fascinating phenomenon, and is heavily studied by the scientific community.

Economic Importance for Humans: Negative

A periodical cicada chorus can become remarkably loud, and is thereby a nuisance to humans. The sheer numbers of a brood can also cause problems, as cicadas fluttering into cars and frightening drivers have caused automobile accidents. The most serious problem related to periodical cicadas is damage to trees. When female Magicicadas cut slits and lay eggs in twigs, the twigs may split, whither, and die. This problem, known as flagging, is not serious for mature trees, but it can greatly harm young trees. Thus, it is recomended that in areas of Magicicada broods, trees not be planted during the year before an expected emergence (Road 1991).

Conservation Status

Although periodical cicadas are not commonly mentioned as threatened species, there is documentation of individuals possibly being harmed by human effects on the environment. During an emergence in a front yard in Chicago in 1990, many of the cicadas had very deformed wings. The use of lawn chemicals was one of the possible explantions for the deformities(Cooley and Marshall 1997). This species is listed as lower risk by the IUCN.

Other Comments

The genus Magicicada contains six species, three with a 17-year life-cycle and three with a 13-year life-cycle. Each 17-year species has a sibling species with the shorter life-cycle. The two species share very similar physical traits, calls and songs, and behaviors. The sibling species of Magicicada septendecim is Magicicada tredecim (Cooley and Marshall 1997).

Contributors

Matthew Gulker (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

native range

the area in which the animal is naturally found, the region in which it is endemic.

suburban

living in residential areas on the outskirts of large cities or towns.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

References

Alexander, R.D. and Moore, T.E. 1962. The Evolutionary Relationships of 17-Year and 13-Year Cicadas, and Three New Species (Homoptera, Cicadidae, Magicicada). Miscellaneous Publications, Museum of Zoology, University of Michigan, No. 121.

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This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.